By way of illustration in laparoscopic operations, it is usually necessary to introduce a fluid and, in particular a gas, such as by way of illustration CO2 into the body cavity into which incision was made in order that the cavity does not collapse due to the “external pressure”.
With increasing duration of the operation, the number of incisions as well as the frequency of changing the instruments requires not only large amounts of insufflation gas, but also high insufflation rates. This is especially the case in HF surgery and laser treatment in which the gas has to remove additionally occurring smoke, etc. In the past, flow rates of a few liters per minute used to suffice, however, for some time increasingly higher flow rates are demanded.
However, even at flow rates in the 5 to 7 l/min range, the patient suffers hyperthermia, i.e. a local drop in temperature distinctly below the body temperature. If (insufflation) devices having even higher outputs, which in the case of the devices that are available on the market reaches up to 15 l/min, or even insufflation devices having flow-through rates up to 40 l/min are employed, as described in the patent literature, the problem of hyperthermia is even more serious than with conventional devices.
Therefore, it has been suggested to provide a means of heating the fluid in the insufflation device. In particular, with gas insufflation devices there is the problem of heating the gas in the insufflation device, because the gas has little thermal capacity, it cools off again in the supply tube on the way to the patient.
Thus, whenever the gas is heated only in the insufflation device, it is necessary to heat the gas to a higher temperature than is actually desired in order that the gas enters the human body “just” at a temperature that corresponds to the body temperature (37° C.). However, this has the drawback that the inertia of the system due to the long tube usually required is large if deviations of the temperature from the desired temperature, i.e. the control constant, is large and therefore the temperature constancy is small due to normal fluctuations. The gas therefore may even be introduced at a too high temperature inside the body.
In another attempt to solve the problem of the patient's hyperthermia, notably a device sold by Wisap, Sauerlach under the name “Flow-Therme” uses an additional heatable tube that connects the actual insufflation device to the instrument to be inserted into the human body.
This solution attempt, too, does not ensure optimum temperature control, because the control constant is large due the length of the tube and the possibly strongly varying surrounding conditions along the tube. Moreover, a heatable tube is less pliant and heavier due to the integrated heating means than a normal tube. Thus, it is not as easy to handle as a normal tube.